The 29-year-old striker signed his deal on Friday and announced it a day later, while thanking OM after five years on the south coast of France.
"I want to thank Olympique Marseille for allowing me to realise my childhood dream," wrote Gignac, who grew up in nearby Martigues before turning professional with Lorient. He joined Marsielle from Toulouse in 2010.
"It gave me such a feeling of accomplishment," he added. This club brings me so much pride, joy and emotion.
"For many of the same reasons, I have decided to choose a new destination, Tigres, which will allow me to pursue my passion in a big football country, Mexico, with an ambitious club who can help me to new successes."
Gignac, capped 19 times by France, had been linked with a number of European clubs, with his decision to head to Mexico coming as a surprise to many observers.
"(Gignac) is now part of our unique family," Tigres said on their own account. "His heart and talent will allow our team to achieve great things."
Gignac scored 77 goals in 186 appearances for Marseille, helping it win the Coupe de la Ligue in 2011 and 2012, as well as the Trophee des Champions in 2011.
